1 files changed, 911 insertions, 281 deletions

diff --git a/fs/configfs/dir.c b/fs/configfs/dir.c
index b668ec61527..668dcabc569 100644
--- a/fs/configfs/dir.c
+++ b/fs/configfs/dir.c
@@ -30,79 +30,212 @@
 #include <linux/mount.h>
 #include <linux/module.h>
 #include <linux/slab.h>
+#include <linux/err.h>
 
 #include <linux/configfs.h>
 #include "configfs_internal.h"
 
 DECLARE_RWSEM(configfs_rename_sem);
+/*
+ * Protects mutations of configfs_dirent linkage together with proper i_mutex
+ * Also protects mutations of symlinks linkage to target configfs_dirent
+ * Mutators of configfs_dirent linkage must *both* have the proper inode locked
+ * and configfs_dirent_lock locked, in that order.
+ * This allows one to safely traverse configfs_dirent trees and symlinks without
+ * having to lock inodes.
+ *
+ * Protects setting of CONFIGFS_USET_DROPPING: checking the flag
+ * unlocked is not reliable unless in detach_groups() called from
+ * rmdir()/unregister() and from configfs_attach_group()
+ */
+DEFINE_SPINLOCK(configfs_dirent_lock);
 
 static void configfs_d_iput(struct dentry * dentry,
 			    struct inode * inode)
 {
-	struct configfs_dirent * sd = dentry->d_fsdata;
+	struct configfs_dirent *sd = dentry->d_fsdata;
 
 	if (sd) {
-		BUG_ON(sd->s_dentry != dentry);
-		sd->s_dentry = NULL;
+		/* Coordinate with configfs_readdir */
+		spin_lock(&configfs_dirent_lock);
+		/* Coordinate with configfs_attach_attr where will increase
+		 * sd->s_count and update sd->s_dentry to new allocated one.
+		 * Only set sd->dentry to null when this dentry is the only
+		 * sd owner.
+		 * If not do so, configfs_d_iput may run just after
+		 * configfs_attach_attr and set sd->s_dentry to null
+		 * even it's still in use.
+		 */
+		if (atomic_read(&sd->s_count) <= 2)
+			sd->s_dentry = NULL;
+
+		spin_unlock(&configfs_dirent_lock);
 		configfs_put(sd);
 	}
 	iput(inode);
 }
 
+const struct dentry_operations configfs_dentry_ops = {
+	.d_iput		= configfs_d_iput,
+	.d_delete	= always_delete_dentry,
+};
+
+#ifdef CONFIG_LOCKDEP
+
 /*
- * We _must_ delete our dentries on last dput, as the chain-to-parent
- * behavior is required to clear the parents of default_groups.
+ * Helpers to make lockdep happy with our recursive locking of default groups'
+ * inodes (see configfs_attach_group() and configfs_detach_group()).
+ * We put default groups i_mutexes in separate classes according to their depth
+ * from the youngest non-default group ancestor.
+ *
+ * For a non-default group A having default groups A/B, A/C, and A/C/D, default
+ * groups A/B and A/C will have their inode's mutex in class
+ * default_group_class[0], and default group A/C/D will be in
+ * default_group_class[1].
+ *
+ * The lock classes are declared and assigned in inode.c, according to the
+ * s_depth value.
+ * The s_depth value is initialized to -1, adjusted to >= 0 when attaching
+ * default groups, and reset to -1 when all default groups are attached. During
+ * attachment, if configfs_create() sees s_depth > 0, the lock class of the new
+ * inode's mutex is set to default_group_class[s_depth - 1].
  */
-static int configfs_d_delete(struct dentry *dentry)
+
+static void configfs_init_dirent_depth(struct configfs_dirent *sd)
 {
-	return 1;
+	sd->s_depth = -1;
 }
 
-static struct dentry_operations configfs_dentry_ops = {
-	.d_iput		= configfs_d_iput,
-	/* simple_delete_dentry() isn't exported */
-	.d_delete	= configfs_d_delete,
-};
+static void configfs_set_dir_dirent_depth(struct configfs_dirent *parent_sd,
+					  struct configfs_dirent *sd)
+{
+	int parent_depth = parent_sd->s_depth;
+
+	if (parent_depth >= 0)
+		sd->s_depth = parent_depth + 1;
+}
+
+static void
+configfs_adjust_dir_dirent_depth_before_populate(struct configfs_dirent *sd)
+{
+	/*
+	 * item's i_mutex class is already setup, so s_depth is now only
+	 * used to set new sub-directories s_depth, which is always done
+	 * with item's i_mutex locked.
+	 */
+	/*
+	 *  sd->s_depth == -1 iff we are a non default group.
+	 *  else (we are a default group) sd->s_depth > 0 (see
+	 *  create_dir()).
+	 */
+	if (sd->s_depth == -1)
+		/*
+		 * We are a non default group and we are going to create
+		 * default groups.
+		 */
+		sd->s_depth = 0;
+}
+
+static void
+configfs_adjust_dir_dirent_depth_after_populate(struct configfs_dirent *sd)
+{
+	/* We will not create default groups anymore. */
+	sd->s_depth = -1;
+}
+
+#else /* CONFIG_LOCKDEP */
+
+static void configfs_init_dirent_depth(struct configfs_dirent *sd)
+{
+}
+
+static void configfs_set_dir_dirent_depth(struct configfs_dirent *parent_sd,
+					  struct configfs_dirent *sd)
+{
+}
+
+static void
+configfs_adjust_dir_dirent_depth_before_populate(struct configfs_dirent *sd)
+{
+}
+
+static void
+configfs_adjust_dir_dirent_depth_after_populate(struct configfs_dirent *sd)
+{
+}
+
+#endif /* CONFIG_LOCKDEP */
 
 /*
  * Allocates a new configfs_dirent and links it to the parent configfs_dirent
  */
-static struct configfs_dirent *configfs_new_dirent(struct configfs_dirent * parent_sd,
-						void * element)
+static struct configfs_dirent *configfs_new_dirent(struct configfs_dirent *parent_sd,
+						   void *element, int type)
 {
 	struct configfs_dirent * sd;
 
-	sd = kmalloc(sizeof(*sd), GFP_KERNEL);
+	sd = kmem_cache_zalloc(configfs_dir_cachep, GFP_KERNEL);
 	if (!sd)
-		return NULL;
+		return ERR_PTR(-ENOMEM);
 
-	memset(sd, 0, sizeof(*sd));
 	atomic_set(&sd->s_count, 1);
 	INIT_LIST_HEAD(&sd->s_links);
 	INIT_LIST_HEAD(&sd->s_children);
-	list_add(&sd->s_sibling, &parent_sd->s_children);
 	sd->s_element = element;
+	sd->s_type = type;
+	configfs_init_dirent_depth(sd);
+	spin_lock(&configfs_dirent_lock);
+	if (parent_sd->s_type & CONFIGFS_USET_DROPPING) {
+		spin_unlock(&configfs_dirent_lock);
+		kmem_cache_free(configfs_dir_cachep, sd);
+		return ERR_PTR(-ENOENT);
+	}
+	list_add(&sd->s_sibling, &parent_sd->s_children);
+	spin_unlock(&configfs_dirent_lock);
 
 	return sd;
 }
 
+/*
+ *
+ * Return -EEXIST if there is already a configfs element with the same
+ * name for the same parent.
+ *
+ * called with parent inode's i_mutex held
+ */
+static int configfs_dirent_exists(struct configfs_dirent *parent_sd,
+				  const unsigned char *new)
+{
+	struct configfs_dirent * sd;
+
+	list_for_each_entry(sd, &parent_sd->s_children, s_sibling) {
+		if (sd->s_element) {
+			const unsigned char *existing = configfs_get_name(sd);
+			if (strcmp(existing, new))
+				continue;
+			else
+				return -EEXIST;
+		}
+	}
+
+	return 0;
+}
+
+
 int configfs_make_dirent(struct configfs_dirent * parent_sd,
 			 struct dentry * dentry, void * element,
 			 umode_t mode, int type)
 {
 	struct configfs_dirent * sd;
 
-	sd = configfs_new_dirent(parent_sd, element);
-	if (!sd)
-		return -ENOMEM;
+	sd = configfs_new_dirent(parent_sd, element, type);
+	if (IS_ERR(sd))
+		return PTR_ERR(sd);
 
 	sd->s_mode = mode;
-	sd->s_type = type;
 	sd->s_dentry = dentry;
-	if (dentry) {
+	if (dentry)
 		dentry->d_fsdata = configfs_get(sd);
-		dentry->d_op = &configfs_dentry_ops;
-	}
 
 	return 0;
 }
@@ -113,11 +246,11 @@ static int init_dir(struct inode * inode)
 	inode->i_fop = &configfs_dir_operations;
 
 	/* directory inodes start off with i_nlink == 2 (for "." entry) */
-	inode->i_nlink++;
+	inc_nlink(inode);
 	return 0;
 }
 
-static int init_file(struct inode * inode)
+static int configfs_init_file(struct inode * inode)
 {
 	inode->i_size = PAGE_SIZE;
 	inode->i_fop = &configfs_file_operations;
@@ -130,19 +263,31 @@ static int init_symlink(struct inode * inode)
 	return 0;
 }
 
-static int create_dir(struct config_item * k, struct dentry * p,
-		      struct dentry * d)
+static int create_dir(struct config_item *k, struct dentry *d)
 {
 	int error;
 	umode_t mode = S_IFDIR| S_IRWXU | S_IRUGO | S_IXUGO;
+	struct dentry *p = d->d_parent;
 
-	error = configfs_create(d, mode, init_dir);
-	if (!error) {
+	BUG_ON(!k);
+
+	error = configfs_dirent_exists(p->d_fsdata, d->d_name.name);
+	if (!error)
 		error = configfs_make_dirent(p->d_fsdata, d, k, mode,
-					   CONFIGFS_DIR);
+					     CONFIGFS_DIR | CONFIGFS_USET_CREATING);
+	if (!error) {
+		configfs_set_dir_dirent_depth(p->d_fsdata, d->d_fsdata);
+		error = configfs_create(d, mode, init_dir);
 		if (!error) {
-			p->d_inode->i_nlink++;
-			(d)->d_op = &configfs_dentry_ops;
+			inc_nlink(p->d_inode);
+		} else {
+			struct configfs_dirent *sd = d->d_fsdata;
+			if (sd) {
+				spin_lock(&configfs_dirent_lock);
+				list_del_init(&sd->s_sibling);
+				spin_unlock(&configfs_dirent_lock);
+				configfs_put(sd);
+			}
 		}
 	}
 	return error;
@@ -153,28 +298,57 @@ static int create_dir(struct config_item * k, struct dentry * p,
  *	configfs_create_dir - create a directory for an config_item.
  *	@item:		config_itemwe're creating directory for.
  *	@dentry:	config_item's dentry.
+ *
+ *	Note: user-created entries won't be allowed under this new directory
+ *	until it is validated by configfs_dir_set_ready()
  */
 
 static int configfs_create_dir(struct config_item * item, struct dentry *dentry)
 {
-	struct dentry * parent;
-	int error = 0;
-
-	BUG_ON(!item);
-
-	if (item->ci_parent)
-		parent = item->ci_parent->ci_dentry;
-	else if (configfs_mount && configfs_mount->mnt_sb)
-		parent = configfs_mount->mnt_sb->s_root;
-	else
-		return -EFAULT;
-
-	error = create_dir(item,parent,dentry);
+	int error = create_dir(item, dentry);
 	if (!error)
 		item->ci_dentry = dentry;
 	return error;
 }
 
+/*
+ * Allow userspace to create new entries under a new directory created with
+ * configfs_create_dir(), and under all of its chidlren directories recursively.
+ * @sd		configfs_dirent of the new directory to validate
+ *
+ * Caller must hold configfs_dirent_lock.
+ */
+static void configfs_dir_set_ready(struct configfs_dirent *sd)
+{
+	struct configfs_dirent *child_sd;
+
+	sd->s_type &= ~CONFIGFS_USET_CREATING;
+	list_for_each_entry(child_sd, &sd->s_children, s_sibling)
+		if (child_sd->s_type & CONFIGFS_USET_CREATING)
+			configfs_dir_set_ready(child_sd);
+}
+
+/*
+ * Check that a directory does not belong to a directory hierarchy being
+ * attached and not validated yet.
+ * @sd		configfs_dirent of the directory to check
+ *
+ * @return	non-zero iff the directory was validated
+ *
+ * Note: takes configfs_dirent_lock, so the result may change from false to true
+ * in two consecutive calls, but never from true to false.
+ */
+int configfs_dirent_is_ready(struct configfs_dirent *sd)
+{
+	int ret;
+
+	spin_lock(&configfs_dirent_lock);
+	ret = !(sd->s_type & CONFIGFS_USET_CREATING);
+	spin_unlock(&configfs_dirent_lock);
+
+	return ret;
+}
+
 int configfs_create_link(struct configfs_symlink *sl,
 			 struct dentry *parent,
 			 struct dentry *dentry)
@@ -182,12 +356,19 @@ int configfs_create_link(struct configfs_symlink *sl,
 	int err = 0;
 	umode_t mode = S_IFLNK | S_IRWXUGO;
 
-	err = configfs_create(dentry, mode, init_symlink);
+	err = configfs_make_dirent(parent->d_fsdata, dentry, sl, mode,
+				   CONFIGFS_ITEM_LINK);
 	if (!err) {
-		err = configfs_make_dirent(parent->d_fsdata, dentry, sl,
-					 mode, CONFIGFS_ITEM_LINK);
-		if (!err)
-			dentry->d_op = &configfs_dentry_ops;
+		err = configfs_create(dentry, mode, init_symlink);
+		if (err) {
+			struct configfs_dirent *sd = dentry->d_fsdata;
+			if (sd) {
+				spin_lock(&configfs_dirent_lock);
+				list_del_init(&sd->s_sibling);
+				spin_unlock(&configfs_dirent_lock);
+				configfs_put(sd);
+			}
+		}
 	}
 	return err;
 }
@@ -198,13 +379,14 @@ static void remove_dir(struct dentry * d)
 	struct configfs_dirent * sd;
 
 	sd = d->d_fsdata;
- 	list_del_init(&sd->s_sibling);
+	spin_lock(&configfs_dirent_lock);
+	list_del_init(&sd->s_sibling);
+	spin_unlock(&configfs_dirent_lock);
 	configfs_put(sd);
 	if (d->d_inode)
 		simple_rmdir(parent->d_inode,d);
 
-	pr_debug(" o %s removing done (%d)\n",d->d_name.name,
-		 atomic_read(&d->d_count));
+	pr_debug(" o %s removing done (%d)\n",d->d_name.name, d_count(d));
 
 	dput(parent);
 }
@@ -216,6 +398,8 @@ static void remove_dir(struct dentry * d)
  * The only thing special about this is that we remove any files in
  * the directory before we remove the directory, and we've inlined
  * what used to be configfs_rmdir() below, instead of calling separately.
+ *
+ * Caller holds the mutex of the item's inode
  */
 
 static void configfs_remove_dir(struct config_item * item)
@@ -241,13 +425,18 @@ static int configfs_attach_attr(struct configfs_dirent * sd, struct dentry * den
 	struct configfs_attribute * attr = sd->s_element;
 	int error;
 
-	error = configfs_create(dentry, (attr->ca_mode & S_IALLUGO) | S_IFREG, init_file);
-	if (error)
-		return error;
-
-	dentry->d_op = &configfs_dentry_ops;
+	spin_lock(&configfs_dirent_lock);
 	dentry->d_fsdata = configfs_get(sd);
 	sd->s_dentry = dentry;
+	spin_unlock(&configfs_dirent_lock);
+
+	error = configfs_create(dentry, (attr->ca_mode & S_IALLUGO) | S_IFREG,
+				configfs_init_file);
+	if (error) {
+		configfs_put(sd);
+		return error;
+	}
+
 	d_rehash(dentry);
 
 	return 0;
@@ -255,12 +444,24 @@ static int configfs_attach_attr(struct configfs_dirent * sd, struct dentry * den
 
 static struct dentry * configfs_lookup(struct inode *dir,
 				       struct dentry *dentry,
-				       struct nameidata *nd)
+				       unsigned int flags)
 {
 	struct configfs_dirent * parent_sd = dentry->d_parent->d_fsdata;
 	struct configfs_dirent * sd;
 	int found = 0;
-	int err = 0;
+	int err;
+
+	/*
+	 * Fake invisibility if dir belongs to a group/default groups hierarchy
+	 * being attached
+	 *
+	 * This forbids userspace to read/write attributes of items which may
+	 * not complete their initialization, since the dentries of the
+	 * attributes won't be instantiated.
+	 */
+	err = -ENOENT;
+	if (!configfs_dirent_is_ready(parent_sd))
+		goto out;
 
 	list_for_each_entry(sd, &parent_sd->s_children, s_sibling) {
 		if (sd->s_type & CONFIGFS_NOT_PINNED) {
@@ -280,42 +481,57 @@ static struct dentry * configfs_lookup(struct inode *dir,
 		 * If it doesn't exist and it isn't a NOT_PINNED item,
 		 * it must be negative.
 		 */
-		return simple_lookup(dir, dentry, nd);
+		if (dentry->d_name.len > NAME_MAX)
+			return ERR_PTR(-ENAMETOOLONG);
+		d_add(dentry, NULL);
+		return NULL;
 	}
 
+out:
 	return ERR_PTR(err);
 }
 
 /*
  * Only subdirectories count here.  Files (CONFIGFS_NOT_PINNED) are
- * attributes and are removed by rmdir().  We recurse, taking i_mutex
- * on all children that are candidates for default detach.  If the
- * result is clean, then configfs_detach_group() will handle dropping
- * i_mutex.  If there is an error, the caller will clean up the i_mutex
- * holders via configfs_detach_rollback().
+ * attributes and are removed by rmdir().  We recurse, setting
+ * CONFIGFS_USET_DROPPING on all children that are candidates for
+ * default detach.
+ * If there is an error, the caller will reset the flags via
+ * configfs_detach_rollback().
  */
-static int configfs_detach_prep(struct dentry *dentry)
+static int configfs_detach_prep(struct dentry *dentry, struct mutex **wait_mutex)
 {
 	struct configfs_dirent *parent_sd = dentry->d_fsdata;
 	struct configfs_dirent *sd;
 	int ret;
 
+	/* Mark that we're trying to drop the group */
+	parent_sd->s_type |= CONFIGFS_USET_DROPPING;
+
 	ret = -EBUSY;
 	if (!list_empty(&parent_sd->s_links))
 		goto out;
 
 	ret = 0;
 	list_for_each_entry(sd, &parent_sd->s_children, s_sibling) {
-		if (sd->s_type & CONFIGFS_NOT_PINNED)
+		if (!sd->s_element ||
+		    (sd->s_type & CONFIGFS_NOT_PINNED))
 			continue;
 		if (sd->s_type & CONFIGFS_USET_DEFAULT) {
-			mutex_lock(&sd->s_dentry->d_inode->i_mutex);
-			/* Mark that we've taken i_mutex */
-			sd->s_type |= CONFIGFS_USET_DROPPING;
+			/* Abort if racing with mkdir() */
+			if (sd->s_type & CONFIGFS_USET_IN_MKDIR) {
+				if (wait_mutex)
+					*wait_mutex = &sd->s_dentry->d_inode->i_mutex;
+				return -EAGAIN;
+			}
 
-			ret = configfs_detach_prep(sd->s_dentry);
+			/*
+			 * Yup, recursive.  If there's a problem, blame
+			 * deep nesting of default_groups
+			 */
+			ret = configfs_detach_prep(sd->s_dentry, wait_mutex);
 			if (!ret)
-			       	continue;
+				continue;
 		} else
 			ret = -ENOTEMPTY;
 
@@ -327,7 +543,7 @@ out:
 }
 
 /*
- * Walk the tree, dropping i_mutex wherever CONFIGFS_USET_DROPPING is
+ * Walk the tree, resetting CONFIGFS_USET_DROPPING wherever it was
  * set.
  */
 static void configfs_detach_rollback(struct dentry *dentry)
@@ -335,16 +551,11 @@ static void configfs_detach_rollback(struct dentry *dentry)
 	struct configfs_dirent *parent_sd = dentry->d_fsdata;
 	struct configfs_dirent *sd;
 
-	list_for_each_entry(sd, &parent_sd->s_children, s_sibling) {
-		if (sd->s_type & CONFIGFS_USET_DEFAULT) {
-			configfs_detach_rollback(sd->s_dentry);
+	parent_sd->s_type &= ~CONFIGFS_USET_DROPPING;
 
-			if (sd->s_type & CONFIGFS_USET_DROPPING) {
-				sd->s_type &= ~CONFIGFS_USET_DROPPING;
-				mutex_unlock(&sd->s_dentry->d_inode->i_mutex);
-			}
-		}
-	}
+	list_for_each_entry(sd, &parent_sd->s_children, s_sibling)
+		if (sd->s_type & CONFIGFS_USET_DEFAULT)
+			configfs_detach_rollback(sd->s_dentry);
 }
 
 static void detach_attrs(struct config_item * item)
@@ -363,7 +574,9 @@ static void detach_attrs(struct config_item * item)
 	list_for_each_entry_safe(sd, tmp, &parent_sd->s_children, s_sibling) {
 		if (!sd->s_element || !(sd->s_type & CONFIGFS_NOT_PINNED))
 			continue;
+		spin_lock(&configfs_dirent_lock);
 		list_del_init(&sd->s_sibling);
+		spin_unlock(&configfs_dirent_lock);
 		configfs_drop_dentry(sd, dentry);
 		configfs_put(sd);
 	}
@@ -419,16 +632,13 @@ static void detach_groups(struct config_group *group)
 
 		child = sd->s_dentry;
 
+		mutex_lock(&child->d_inode->i_mutex);
+
 		configfs_detach_group(sd->s_element);
 		child->d_inode->i_flags |= S_DEAD;
+		dont_mount(child);
 
-		/*
-		 * From rmdir/unregister, a configfs_detach_prep() pass
-		 * has taken our i_mutex for us.  Drop it.
-		 * From mkdir/register cleanup, there is no sem held.
-		 */
-		if (sd->s_type & CONFIGFS_USET_DROPPING)
-			mutex_unlock(&child->d_inode->i_mutex);
+		mutex_unlock(&child->d_inode->i_mutex);
 
 		d_delete(child);
 		dput(child);
@@ -452,19 +662,15 @@ static int create_default_group(struct config_group *parent_group,
 				struct config_group *group)
 {
 	int ret;
-	struct qstr name;
 	struct configfs_dirent *sd;
 	/* We trust the caller holds a reference to parent */
 	struct dentry *child, *parent = parent_group->cg_item.ci_dentry;
 
 	if (!group->cg_item.ci_name)
 		group->cg_item.ci_name = group->cg_item.ci_namebuf;
-	name.name = group->cg_item.ci_name;
-	name.len = strlen(name.name);
-	name.hash = full_name_hash(name.name, name.len);
 
 	ret = -ENOMEM;
-	child = d_alloc(parent, &name);
+	child = d_alloc_name(parent, group->cg_item.ci_name);
 	if (child) {
 		d_add(child, NULL);
 
@@ -474,7 +680,8 @@ static int create_default_group(struct config_group *parent_group,
 			sd = child->d_fsdata;
 			sd->s_type |= CONFIGFS_USET_DEFAULT;
 		} else {
-			d_delete(child);
+			BUG_ON(child->d_inode);
+			d_drop(child);
 			dput(child);
 		}
 	}
@@ -485,40 +692,27 @@ static int create_default_group(struct config_group *parent_group,
 static int populate_groups(struct config_group *group)
 {
 	struct config_group *new_group;
-	struct dentry *dentry = group->cg_item.ci_dentry;
 	int ret = 0;
 	int i;
 
-	if (group && group->default_groups) {
-		/* FYI, we're faking mkdir here
-		 * I'm not sure we need this semaphore, as we're called
-		 * from our parent's mkdir.  That holds our parent's
-		 * i_mutex, so afaik lookup cannot continue through our
-		 * parent to find us, let alone mess with our tree.
-		 * That said, taking our i_mutex is closer to mkdir
-		 * emulation, and shouldn't hurt. */
-		mutex_lock(&dentry->d_inode->i_mutex);
-
+	if (group->default_groups) {
 		for (i = 0; group->default_groups[i]; i++) {
 			new_group = group->default_groups[i];
 
 			ret = create_default_group(group, new_group);
-			if (ret)
+			if (ret) {
+				detach_groups(group);
 				break;
+			}
 		}
-
-		mutex_unlock(&dentry->d_inode->i_mutex);
 	}
 
-	if (ret)
-		detach_groups(group);
-
 	return ret;
 }
 
 /*
  * All of link_obj/unlink_obj/link_group/unlink_group require that
- * subsys->su_sem is held.
+ * subsys->su_mutex is held.
  */
 
 static void unlink_obj(struct config_item *item)
@@ -531,20 +725,34 @@ static void unlink_obj(struct config_item *item)
 
 		item->ci_group = NULL;
 		item->ci_parent = NULL;
+
+		/* Drop the reference for ci_entry */
 		config_item_put(item);
 
+		/* Drop the reference for ci_parent */
 		config_group_put(group);
 	}
 }
 
 static void link_obj(struct config_item *parent_item, struct config_item *item)
 {
-	/* Parent seems redundant with group, but it makes certain
-	 * traversals much nicer. */
+	/*
+	 * Parent seems redundant with group, but it makes certain
+	 * traversals much nicer.
+	 */
 	item->ci_parent = parent_item;
+
+	/*
+	 * We hold a reference on the parent for the child's ci_parent
+	 * link.
+	 */
 	item->ci_group = config_group_get(to_config_group(parent_item));
 	list_add_tail(&item->ci_entry, &item->ci_group->cg_children);
 
+	/*
+	 * We hold a reference on the child for ci_entry on the parent's
+	 * cg_children
+	 */
 	config_item_get(item);
 }
 
@@ -613,7 +821,16 @@ static int configfs_attach_item(struct config_item *parent_item,
 	if (!ret) {
 		ret = populate_attrs(item);
 		if (ret) {
+			/*
+			 * We are going to remove an inode and its dentry but
+			 * the VFS may already have hit and used them. Thus,
+			 * we must lock them as rmdir() would.
+			 */
+			mutex_lock(&dentry->d_inode->i_mutex);
 			configfs_remove_dir(item);
+			dentry->d_inode->i_flags |= S_DEAD;
+			dont_mount(dentry);
+			mutex_unlock(&dentry->d_inode->i_mutex);
 			d_delete(dentry);
 		}
 	}
@@ -621,6 +838,7 @@ static int configfs_attach_item(struct config_item *parent_item,
 	return ret;
 }
 
+/* Caller holds the mutex of the item's inode */
 static void configfs_detach_item(struct config_item *item)
 {
 	detach_attrs(item);
@@ -639,16 +857,33 @@ static int configfs_attach_group(struct config_item *parent_item,
 		sd = dentry->d_fsdata;
 		sd->s_type |= CONFIGFS_USET_DIR;
 
+		/*
+		 * FYI, we're faking mkdir in populate_groups()
+		 * We must lock the group's inode to avoid races with the VFS
+		 * which can already hit the inode and try to add/remove entries
+		 * under it.
+		 *
+		 * We must also lock the inode to remove it safely in case of
+		 * error, as rmdir() would.
+		 */
+		mutex_lock_nested(&dentry->d_inode->i_mutex, I_MUTEX_CHILD);
+		configfs_adjust_dir_dirent_depth_before_populate(sd);
 		ret = populate_groups(to_config_group(item));
 		if (ret) {
 			configfs_detach_item(item);
-			d_delete(dentry);
+			dentry->d_inode->i_flags |= S_DEAD;
+			dont_mount(dentry);
 		}
+		configfs_adjust_dir_dirent_depth_after_populate(sd);
+		mutex_unlock(&dentry->d_inode->i_mutex);
+		if (ret)
+			d_delete(dentry);
 	}
 
 	return ret;
 }
 
+/* Caller holds the mutex of the group's inode */
 static void configfs_detach_group(struct config_item *item)
 {
 	detach_groups(to_config_group(item));
@@ -656,6 +891,28 @@ static void configfs_detach_group(struct config_item *item)
 }
 
 /*
+ * After the item has been detached from the filesystem view, we are
+ * ready to tear it out of the hierarchy.  Notify the client before
+ * we do that so they can perform any cleanup that requires
+ * navigating the hierarchy.  A client does not need to provide this
+ * callback.  The subsystem semaphore MUST be held by the caller, and
+ * references must be valid for both items.  It also assumes the
+ * caller has validated ci_type.
+ */
+static void client_disconnect_notify(struct config_item *parent_item,
+				     struct config_item *item)
+{
+	struct config_item_type *type;
+
+	type = parent_item->ci_type;
+	BUG_ON(!type);
+
+	if (type->ct_group_ops && type->ct_group_ops->disconnect_notify)
+		type->ct_group_ops->disconnect_notify(to_config_group(parent_item),
+						      item);
+}
+
+/*
  * Drop the initial reference from make_item()/make_group()
  * This function assumes that reference is held on item
  * and that item holds a valid reference to the parent.  Also, it
@@ -669,33 +926,270 @@ static void client_drop_item(struct config_item *parent_item,
 	type = parent_item->ci_type;
 	BUG_ON(!type);
 
+	/*
+	 * If ->drop_item() exists, it is responsible for the
+	 * config_item_put().
+	 */
 	if (type->ct_group_ops && type->ct_group_ops->drop_item)
 		type->ct_group_ops->drop_item(to_config_group(parent_item),
-						item);
+					      item);
 	else
 		config_item_put(item);
 }
 
+#ifdef DEBUG
+static void configfs_dump_one(struct configfs_dirent *sd, int level)
+{
+	pr_info("%*s\"%s\":\n", level, " ", configfs_get_name(sd));
+
+#define type_print(_type) if (sd->s_type & _type) pr_info("%*s %s\n", level, " ", #_type);
+	type_print(CONFIGFS_ROOT);
+	type_print(CONFIGFS_DIR);
+	type_print(CONFIGFS_ITEM_ATTR);
+	type_print(CONFIGFS_ITEM_LINK);
+	type_print(CONFIGFS_USET_DIR);
+	type_print(CONFIGFS_USET_DEFAULT);
+	type_print(CONFIGFS_USET_DROPPING);
+#undef type_print
+}
+
+static int configfs_dump(struct configfs_dirent *sd, int level)
+{
+	struct configfs_dirent *child_sd;
+	int ret = 0;
+
+	configfs_dump_one(sd, level);
+
+	if (!(sd->s_type & (CONFIGFS_DIR|CONFIGFS_ROOT)))
+		return 0;
+
+	list_for_each_entry(child_sd, &sd->s_children, s_sibling) {
+		ret = configfs_dump(child_sd, level + 2);
+		if (ret)
+			break;
+	}
+
+	return ret;
+}
+#endif
+
+
+/*
+ * configfs_depend_item() and configfs_undepend_item()
+ *
+ * WARNING: Do not call these from a configfs callback!
+ *
+ * This describes these functions and their helpers.
+ *
+ * Allow another kernel system to depend on a config_item.  If this
+ * happens, the item cannot go away until the dependent can live without
+ * it.  The idea is to give client modules as simple an interface as
+ * possible.  When a system asks them to depend on an item, they just
+ * call configfs_depend_item().  If the item is live and the client
+ * driver is in good shape, we'll happily do the work for them.
+ *
+ * Why is the locking complex?  Because configfs uses the VFS to handle
+ * all locking, but this function is called outside the normal
+ * VFS->configfs path.  So it must take VFS locks to prevent the
+ * VFS->configfs stuff (configfs_mkdir(), configfs_rmdir(), etc).  This is
+ * why you can't call these functions underneath configfs callbacks.
+ *
+ * Note, btw, that this can be called at *any* time, even when a configfs
+ * subsystem isn't registered, or when configfs is loading or unloading.
+ * Just like configfs_register_subsystem().  So we take the same
+ * precautions.  We pin the filesystem.  We lock configfs_dirent_lock.
+ * If we can find the target item in the
+ * configfs tree, it must be part of the subsystem tree as well, so we
+ * do not need the subsystem semaphore.  Holding configfs_dirent_lock helps
+ * locking out mkdir() and rmdir(), who might be racing us.
+ */
+
+/*
+ * configfs_depend_prep()
+ *
+ * Only subdirectories count here.  Files (CONFIGFS_NOT_PINNED) are
+ * attributes.  This is similar but not the same to configfs_detach_prep().
+ * Note that configfs_detach_prep() expects the parent to be locked when it
+ * is called, but we lock the parent *inside* configfs_depend_prep().  We
+ * do that so we can unlock it if we find nothing.
+ *
+ * Here we do a depth-first search of the dentry hierarchy looking for
+ * our object.
+ * We deliberately ignore items tagged as dropping since they are virtually
+ * dead, as well as items in the middle of attachment since they virtually
+ * do not exist yet. This completes the locking out of racing mkdir() and
+ * rmdir().
+ * Note: subdirectories in the middle of attachment start with s_type =
+ * CONFIGFS_DIR|CONFIGFS_USET_CREATING set by create_dir().  When
+ * CONFIGFS_USET_CREATING is set, we ignore the item.  The actual set of
+ * s_type is in configfs_new_dirent(), which has configfs_dirent_lock.
+ *
+ * If the target is not found, -ENOENT is bubbled up.
+ *
+ * This adds a requirement that all config_items be unique!
+ *
+ * This is recursive.  There isn't
+ * much on the stack, though, so folks that need this function - be careful
+ * about your stack!  Patches will be accepted to make it iterative.
+ */
+static int configfs_depend_prep(struct dentry *origin,
+				struct config_item *target)
+{
+	struct configfs_dirent *child_sd, *sd;
+	int ret = 0;
+
+	BUG_ON(!origin || !origin->d_fsdata);
+	sd = origin->d_fsdata;
 
-static int configfs_mkdir(struct inode *dir, struct dentry *dentry, int mode)
+	if (sd->s_element == target)  /* Boo-yah */
+		goto out;
+
+	list_for_each_entry(child_sd, &sd->s_children, s_sibling) {
+		if ((child_sd->s_type & CONFIGFS_DIR) &&
+		    !(child_sd->s_type & CONFIGFS_USET_DROPPING) &&
+		    !(child_sd->s_type & CONFIGFS_USET_CREATING)) {
+			ret = configfs_depend_prep(child_sd->s_dentry,
+						   target);
+			if (!ret)
+				goto out;  /* Child path boo-yah */
+		}
+	}
+
+	/* We looped all our children and didn't find target */
+	ret = -ENOENT;
+
+out:
+	return ret;
+}
+
+int configfs_depend_item(struct configfs_subsystem *subsys,
+			 struct config_item *target)
 {
 	int ret;
-	struct config_group *group;
-	struct config_item *item;
+	struct configfs_dirent *p, *root_sd, *subsys_sd = NULL;
+	struct config_item *s_item = &subsys->su_group.cg_item;
+	struct dentry *root;
+
+	/*
+	 * Pin the configfs filesystem.  This means we can safely access
+	 * the root of the configfs filesystem.
+	 */
+	root = configfs_pin_fs();
+	if (IS_ERR(root))
+		return PTR_ERR(root);
+
+	/*
+	 * Next, lock the root directory.  We're going to check that the
+	 * subsystem is really registered, and so we need to lock out
+	 * configfs_[un]register_subsystem().
+	 */
+	mutex_lock(&root->d_inode->i_mutex);
+
+	root_sd = root->d_fsdata;
+
+	list_for_each_entry(p, &root_sd->s_children, s_sibling) {
+		if (p->s_type & CONFIGFS_DIR) {
+			if (p->s_element == s_item) {
+				subsys_sd = p;
+				break;
+			}
+		}
+	}
+
+	if (!subsys_sd) {
+		ret = -ENOENT;
+		goto out_unlock_fs;
+	}
+
+	/* Ok, now we can trust subsys/s_item */
+
+	spin_lock(&configfs_dirent_lock);
+	/* Scan the tree, return 0 if found */
+	ret = configfs_depend_prep(subsys_sd->s_dentry, target);
+	if (ret)
+		goto out_unlock_dirent_lock;
+
+	/*
+	 * We are sure that the item is not about to be removed by rmdir(), and
+	 * not in the middle of attachment by mkdir().
+	 */
+	p = target->ci_dentry->d_fsdata;
+	p->s_dependent_count += 1;
+
+out_unlock_dirent_lock:
+	spin_unlock(&configfs_dirent_lock);
+out_unlock_fs:
+	mutex_unlock(&root->d_inode->i_mutex);
+
+	/*
+	 * If we succeeded, the fs is pinned via other methods.  If not,
+	 * we're done with it anyway.  So release_fs() is always right.
+	 */
+	configfs_release_fs();
+
+	return ret;
+}
+EXPORT_SYMBOL(configfs_depend_item);
+
+/*
+ * Release the dependent linkage.  This is much simpler than
+ * configfs_depend_item() because we know that that the client driver is
+ * pinned, thus the subsystem is pinned, and therefore configfs is pinned.
+ */
+void configfs_undepend_item(struct configfs_subsystem *subsys,
+			    struct config_item *target)
+{
+	struct configfs_dirent *sd;
+
+	/*
+	 * Since we can trust everything is pinned, we just need
+	 * configfs_dirent_lock.
+	 */
+	spin_lock(&configfs_dirent_lock);
+
+	sd = target->ci_dentry->d_fsdata;
+	BUG_ON(sd->s_dependent_count < 1);
+
+	sd->s_dependent_count -= 1;
+
+	/*
+	 * After this unlock, we cannot trust the item to stay alive!
+	 * DO NOT REFERENCE item after this unlock.
+	 */
+	spin_unlock(&configfs_dirent_lock);
+}
+EXPORT_SYMBOL(configfs_undepend_item);
+
+static int configfs_mkdir(struct inode *dir, struct dentry *dentry, umode_t mode)
+{
+	int ret = 0;
+	int module_got = 0;
+	struct config_group *group = NULL;
+	struct config_item *item = NULL;
 	struct config_item *parent_item;
 	struct configfs_subsystem *subsys;
 	struct configfs_dirent *sd;
 	struct config_item_type *type;
-	struct module *owner;
+	struct module *subsys_owner = NULL, *new_item_owner = NULL;
 	char *name;
 
-	if (dentry->d_parent == configfs_sb->s_root)
-		return -EPERM;
-
 	sd = dentry->d_parent->d_fsdata;
-	if (!(sd->s_type & CONFIGFS_USET_DIR))
-		return -EPERM;
 
+	/*
+	 * Fake invisibility if dir belongs to a group/default groups hierarchy
+	 * being attached
+	 */
+	if (!configfs_dirent_is_ready(sd)) {
+		ret = -ENOENT;
+		goto out;
+	}
+
+	if (!(sd->s_type & CONFIGFS_USET_DIR)) {
+		ret = -EPERM;
+		goto out;
+	}
+
+	/* Get a working ref for the duration of this function */
 	parent_item = configfs_get_config_item(dentry->d_parent);
 	type = parent_item->ci_type;
 	subsys = to_config_group(parent_item)->cg_subsys;
@@ -704,69 +1198,140 @@ static int configfs_mkdir(struct inode *dir, struct dentry *dentry, int mode)
 	if (!type || !type->ct_group_ops ||
 	    (!type->ct_group_ops->make_group &&
 	     !type->ct_group_ops->make_item)) {
-		config_item_put(parent_item);
-		return -EPERM;  /* What lack-of-mkdir returns */
+		ret = -EPERM;  /* Lack-of-mkdir returns -EPERM */
+		goto out_put;
+	}
+
+	/*
+	 * The subsystem may belong to a different module than the item
+	 * being created.  We don't want to safely pin the new item but
+	 * fail to pin the subsystem it sits under.
+	 */
+	if (!subsys->su_group.cg_item.ci_type) {
+		ret = -EINVAL;
+		goto out_put;
+	}
+	subsys_owner = subsys->su_group.cg_item.ci_type->ct_owner;
+	if (!try_module_get(subsys_owner)) {
+		ret = -EINVAL;
+		goto out_put;
 	}
 
 	name = kmalloc(dentry->d_name.len + 1, GFP_KERNEL);
 	if (!name) {
-		config_item_put(parent_item);
-		return -ENOMEM;
+		ret = -ENOMEM;
+		goto out_subsys_put;
 	}
+
 	snprintf(name, dentry->d_name.len + 1, "%s", dentry->d_name.name);
 
-	down(&subsys->su_sem);
-	group = NULL;
-	item = NULL;
+	mutex_lock(&subsys->su_mutex);
 	if (type->ct_group_ops->make_group) {
 		group = type->ct_group_ops->make_group(to_config_group(parent_item), name);
-		if (group) {
+		if (!group)
+			group = ERR_PTR(-ENOMEM);
+		if (!IS_ERR(group)) {
 			link_group(to_config_group(parent_item), group);
 			item = &group->cg_item;
-		}
+		} else
+			ret = PTR_ERR(group);
 	} else {
 		item = type->ct_group_ops->make_item(to_config_group(parent_item), name);
-		if (item)
+		if (!item)
+			item = ERR_PTR(-ENOMEM);
+		if (!IS_ERR(item))
 			link_obj(parent_item, item);
+		else
+			ret = PTR_ERR(item);
 	}
-	up(&subsys->su_sem);
+	mutex_unlock(&subsys->su_mutex);
 
 	kfree(name);
-	if (!item) {
-		config_item_put(parent_item);
-		return -ENOMEM;
+	if (ret) {
+		/*
+		 * If ret != 0, then link_obj() was never called.
+		 * There are no extra references to clean up.
+		 */
+		goto out_subsys_put;
 	}
 
-	ret = -EINVAL;
+	/*
+	 * link_obj() has been called (via link_group() for groups).
+	 * From here on out, errors must clean that up.
+	 */
+
 	type = item->ci_type;
-	if (type) {
-		owner = type->ct_owner;
-		if (try_module_get(owner)) {
-			if (group) {
-				ret = configfs_attach_group(parent_item,
-							    item,
-							    dentry);
-			} else {
-				ret = configfs_attach_item(parent_item,
-							   item,
-							   dentry);
-			}
+	if (!type) {
+		ret = -EINVAL;
+		goto out_unlink;
+	}
 
-			if (ret) {
-				down(&subsys->su_sem);
-				if (group)
-					unlink_group(group);
-				else
-					unlink_obj(item);
-				client_drop_item(parent_item, item);
-				up(&subsys->su_sem);
+	new_item_owner = type->ct_owner;
+	if (!try_module_get(new_item_owner)) {
+		ret = -EINVAL;
+		goto out_unlink;
+	}
 
-				config_item_put(parent_item);
-				module_put(owner);
-			}
-		}
+	/*
+	 * I hate doing it this way, but if there is
+	 * an error,  module_put() probably should
+	 * happen after any cleanup.
+	 */
+	module_got = 1;
+
+	/*
+	 * Make racing rmdir() fail if it did not tag parent with
+	 * CONFIGFS_USET_DROPPING
+	 * Note: if CONFIGFS_USET_DROPPING is already set, attach_group() will
+	 * fail and let rmdir() terminate correctly
+	 */
+	spin_lock(&configfs_dirent_lock);
+	/* This will make configfs_detach_prep() fail */
+	sd->s_type |= CONFIGFS_USET_IN_MKDIR;
+	spin_unlock(&configfs_dirent_lock);
+
+	if (group)
+		ret = configfs_attach_group(parent_item, item, dentry);
+	else
+		ret = configfs_attach_item(parent_item, item, dentry);
+
+	spin_lock(&configfs_dirent_lock);
+	sd->s_type &= ~CONFIGFS_USET_IN_MKDIR;
+	if (!ret)
+		configfs_dir_set_ready(dentry->d_fsdata);
+	spin_unlock(&configfs_dirent_lock);
+
+out_unlink:
+	if (ret) {
+		/* Tear down everything we built up */
+		mutex_lock(&subsys->su_mutex);
+
+		client_disconnect_notify(parent_item, item);
+		if (group)
+			unlink_group(group);
+		else
+			unlink_obj(item);
+		client_drop_item(parent_item, item);
+
+		mutex_unlock(&subsys->su_mutex);
+
+		if (module_got)
+			module_put(new_item_owner);
 	}
 
+out_subsys_put:
+	if (ret)
+		module_put(subsys_owner);
+
+out_put:
+	/*
+	 * link_obj()/link_group() took a reference from child->parent,
+	 * so the parent is safely pinned.  We can drop our working
+	 * reference.
+	 */
+	config_item_put(parent_item);
+
+out:
 	return ret;
 }
 
@@ -776,16 +1341,14 @@ static int configfs_rmdir(struct inode *dir, struct dentry *dentry)
 	struct config_item *item;
 	struct configfs_subsystem *subsys;
 	struct configfs_dirent *sd;
-	struct module *owner = NULL;
+	struct module *subsys_owner = NULL, *dead_item_owner = NULL;
 	int ret;
 
-	if (dentry->d_parent == configfs_sb->s_root)
-		return -EPERM;
-
 	sd = dentry->d_fsdata;
 	if (sd->s_type & CONFIGFS_USET_DEFAULT)
 		return -EPERM;
 
+	/* Get a working ref until we have the child */
 	parent_item = configfs_get_config_item(dentry->d_parent);
 	subsys = to_config_group(parent_item)->cg_subsys;
 	BUG_ON(!subsys);
@@ -795,50 +1358,92 @@ static int configfs_rmdir(struct inode *dir, struct dentry *dentry)
 		return -EINVAL;
 	}
 
-	ret = configfs_detach_prep(dentry);
-	if (ret) {
-		configfs_detach_rollback(dentry);
-		config_item_put(parent_item);
-		return ret;
-	}
+	/* configfs_mkdir() shouldn't have allowed this */
+	BUG_ON(!subsys->su_group.cg_item.ci_type);
+	subsys_owner = subsys->su_group.cg_item.ci_type->ct_owner;
+
+	/*
+	 * Ensure that no racing symlink() will make detach_prep() fail while
+	 * the new link is temporarily attached
+	 */
+	do {
+		struct mutex *wait_mutex;
 
+		mutex_lock(&configfs_symlink_mutex);
+		spin_lock(&configfs_dirent_lock);
+		/*
+		 * Here's where we check for dependents.  We're protected by
+		 * configfs_dirent_lock.
+		 * If no dependent, atomically tag the item as dropping.
+		 */
+		ret = sd->s_dependent_count ? -EBUSY : 0;
+		if (!ret) {
+			ret = configfs_detach_prep(dentry, &wait_mutex);
+			if (ret)
+				configfs_detach_rollback(dentry);
+		}
+		spin_unlock(&configfs_dirent_lock);
+		mutex_unlock(&configfs_symlink_mutex);
+
+		if (ret) {
+			if (ret != -EAGAIN) {
+				config_item_put(parent_item);
+				return ret;
+			}
+
+			/* Wait until the racing operation terminates */
+			mutex_lock(wait_mutex);
+			mutex_unlock(wait_mutex);
+		}
+	} while (ret == -EAGAIN);
+
+	/* Get a working ref for the duration of this function */
 	item = configfs_get_config_item(dentry);
 
 	/* Drop reference from above, item already holds one. */
 	config_item_put(parent_item);
 
 	if (item->ci_type)
-		owner = item->ci_type->ct_owner;
+		dead_item_owner = item->ci_type->ct_owner;
 
 	if (sd->s_type & CONFIGFS_USET_DIR) {
 		configfs_detach_group(item);
 
-		down(&subsys->su_sem);
+		mutex_lock(&subsys->su_mutex);
+		client_disconnect_notify(parent_item, item);
 		unlink_group(to_config_group(item));
 	} else {
 		configfs_detach_item(item);
 
-		down(&subsys->su_sem);
+		mutex_lock(&subsys->su_mutex);
+		client_disconnect_notify(parent_item, item);
 		unlink_obj(item);
 	}
 
 	client_drop_item(parent_item, item);
-	up(&subsys->su_sem);
+	mutex_unlock(&subsys->su_mutex);
 
 	/* Drop our reference from above */
 	config_item_put(item);
 
-	module_put(owner);
+	module_put(dead_item_owner);
+	module_put(subsys_owner);
 
 	return 0;
 }
 
-struct inode_operations configfs_dir_inode_operations = {
+const struct inode_operations configfs_dir_inode_operations = {
 	.mkdir		= configfs_mkdir,
 	.rmdir		= configfs_rmdir,
 	.symlink	= configfs_symlink,
 	.unlink		= configfs_unlink,
 	.lookup		= configfs_lookup,
+	.setattr	= configfs_setattr,
+};
+
+const struct inode_operations configfs_root_inode_operations = {
+	.lookup		= configfs_lookup,
+	.setattr	= configfs_setattr,
 };
 
 #if 0
@@ -860,7 +1465,7 @@ int configfs_rename_dir(struct config_item * item, const char *new_name)
 
 	new_dentry = lookup_one_len(new_name, parent, strlen(new_name));
 	if (!IS_ERR(new_dentry)) {
-  		if (!new_dentry->d_inode) {
+		if (!new_dentry->d_inode) {
 			error = config_item_set_name(item, "%s", new_name);
 			if (!error) {
 				d_add(new_dentry, NULL);
@@ -881,24 +1486,37 @@ int configfs_rename_dir(struct config_item * item, const char *new_name)
 
 static int configfs_dir_open(struct inode *inode, struct file *file)
 {
-	struct dentry * dentry = file->f_dentry;
+	struct dentry * dentry = file->f_path.dentry;
 	struct configfs_dirent * parent_sd = dentry->d_fsdata;
+	int err;
 
 	mutex_lock(&dentry->d_inode->i_mutex);
-	file->private_data = configfs_new_dirent(parent_sd, NULL);
+	/*
+	 * Fake invisibility if dir belongs to a group/default groups hierarchy
+	 * being attached
+	 */
+	err = -ENOENT;
+	if (configfs_dirent_is_ready(parent_sd)) {
+		file->private_data = configfs_new_dirent(parent_sd, NULL, 0);
+		if (IS_ERR(file->private_data))
+			err = PTR_ERR(file->private_data);
+		else
+			err = 0;
+	}
 	mutex_unlock(&dentry->d_inode->i_mutex);
 
-	return file->private_data ? 0 : -ENOMEM;
-
+	return err;
 }
 
 static int configfs_dir_close(struct inode *inode, struct file *file)
 {
-	struct dentry * dentry = file->f_dentry;
+	struct dentry * dentry = file->f_path.dentry;
 	struct configfs_dirent * cursor = file->private_data;
 
 	mutex_lock(&dentry->d_inode->i_mutex);
+	spin_lock(&configfs_dirent_lock);
 	list_del_init(&cursor->s_sibling);
+	spin_unlock(&configfs_dirent_lock);
 	mutex_unlock(&dentry->d_inode->i_mutex);
 
 	release_configfs_dirent(cursor);
@@ -912,78 +1530,83 @@ static inline unsigned char dt_type(struct configfs_dirent *sd)
 	return (sd->s_mode >> 12) & 15;
 }
 
-static int configfs_readdir(struct file * filp, void * dirent, filldir_t filldir)
+static int configfs_readdir(struct file *file, struct dir_context *ctx)
 {
-	struct dentry *dentry = filp->f_dentry;
+	struct dentry *dentry = file->f_path.dentry;
+	struct super_block *sb = dentry->d_sb;
 	struct configfs_dirent * parent_sd = dentry->d_fsdata;
-	struct configfs_dirent *cursor = filp->private_data;
+	struct configfs_dirent *cursor = file->private_data;
 	struct list_head *p, *q = &cursor->s_sibling;
-	ino_t ino;
-	int i = filp->f_pos;
+	ino_t ino = 0;
+
+	if (!dir_emit_dots(file, ctx))
+		return 0;
+	if (ctx->pos == 2) {
+		spin_lock(&configfs_dirent_lock);
+		list_move(q, &parent_sd->s_children);
+		spin_unlock(&configfs_dirent_lock);
+	}
+	for (p = q->next; p != &parent_sd->s_children; p = p->next) {
+		struct configfs_dirent *next;
+		const char *name;
+		int len;
+		struct inode *inode = NULL;
+
+		next = list_entry(p, struct configfs_dirent, s_sibling);
+		if (!next->s_element)
+			continue;
 
-	switch (i) {
-		case 0:
-			ino = dentry->d_inode->i_ino;
-			if (filldir(dirent, ".", 1, i, ino, DT_DIR) < 0)
-				break;
-			filp->f_pos++;
-			i++;
-			/* fallthrough */
-		case 1:
-			ino = parent_ino(dentry);
-			if (filldir(dirent, "..", 2, i, ino, DT_DIR) < 0)
-				break;
-			filp->f_pos++;
-			i++;
-			/* fallthrough */
-		default:
-			if (filp->f_pos == 2) {
-				list_del(q);
-				list_add(q, &parent_sd->s_children);
-			}
-			for (p=q->next; p!= &parent_sd->s_children; p=p->next) {
-				struct configfs_dirent *next;
-				const char * name;
-				int len;
+		name = configfs_get_name(next);
+		len = strlen(name);
 
-				next = list_entry(p, struct configfs_dirent,
-						   s_sibling);
-				if (!next->s_element)
-					continue;
-
-				name = configfs_get_name(next);
-				len = strlen(name);
-				if (next->s_dentry)
-					ino = next->s_dentry->d_inode->i_ino;
-				else
-					ino = iunique(configfs_sb, 2);
-
-				if (filldir(dirent, name, len, filp->f_pos, ino,
-						 dt_type(next)) < 0)
-					return 0;
-
-				list_del(q);
-				list_add(q, p);
-				p = q;
-				filp->f_pos++;
-			}
+		/*
+		 * We'll have a dentry and an inode for
+		 * PINNED items and for open attribute
+		 * files.  We lock here to prevent a race
+		 * with configfs_d_iput() clearing
+		 * s_dentry before calling iput().
+		 *
+		 * Why do we go to the trouble?  If
+		 * someone has an attribute file open,
+		 * the inode number should match until
+		 * they close it.  Beyond that, we don't
+		 * care.
+		 */
+		spin_lock(&configfs_dirent_lock);
+		dentry = next->s_dentry;
+		if (dentry)
+			inode = dentry->d_inode;
+		if (inode)
+			ino = inode->i_ino;
+		spin_unlock(&configfs_dirent_lock);
+		if (!inode)
+			ino = iunique(sb, 2);
+
+		if (!dir_emit(ctx, name, len, ino, dt_type(next)))
+			return 0;
+
+		spin_lock(&configfs_dirent_lock);
+		list_move(q, p);
+		spin_unlock(&configfs_dirent_lock);
+		p = q;
+		ctx->pos++;
 	}
 	return 0;
 }
 
-static loff_t configfs_dir_lseek(struct file * file, loff_t offset, int origin)
+static loff_t configfs_dir_lseek(struct file *file, loff_t offset, int whence)
 {
-	struct dentry * dentry = file->f_dentry;
+	struct dentry * dentry = file->f_path.dentry;
 
 	mutex_lock(&dentry->d_inode->i_mutex);
-	switch (origin) {
+	switch (whence) {
 		case 1:
 			offset += file->f_pos;
 		case 0:
 			if (offset >= 0)
 				break;
 		default:
-			mutex_unlock(&file->f_dentry->d_inode->i_mutex);
+			mutex_unlock(&file_inode(file)->i_mutex);
 			return -EINVAL;
 	}
 	if (offset != file->f_pos) {
@@ -994,6 +1617,7 @@ static loff_t configfs_dir_lseek(struct file * file, loff_t offset, int origin)
 			struct list_head *p;
 			loff_t n = file->f_pos - 2;
 
+			spin_lock(&configfs_dirent_lock);
 			list_del(&cursor->s_sibling);
 			p = sd->s_children.next;
 			while (n && p != &sd->s_children) {
@@ -1005,65 +1629,64 @@ static loff_t configfs_dir_lseek(struct file * file, loff_t offset, int origin)
 				p = p->next;
 			}
 			list_add_tail(&cursor->s_sibling, p);
+			spin_unlock(&configfs_dirent_lock);
 		}
 	}
 	mutex_unlock(&dentry->d_inode->i_mutex);
 	return offset;
 }
 
-struct file_operations configfs_dir_operations = {
+const struct file_operations configfs_dir_operations = {
 	.open		= configfs_dir_open,
 	.release	= configfs_dir_close,
 	.llseek		= configfs_dir_lseek,
 	.read		= generic_read_dir,
-	.readdir	= configfs_readdir,
+	.iterate	= configfs_readdir,
 };
 
 int configfs_register_subsystem(struct configfs_subsystem *subsys)
 {
 	int err;
 	struct config_group *group = &subsys->su_group;
-	struct qstr name;
 	struct dentry *dentry;
+	struct dentry *root;
 	struct configfs_dirent *sd;
 
-	err = configfs_pin_fs();
-	if (err)
-		return err;
+	root = configfs_pin_fs();
+	if (IS_ERR(root))
+		return PTR_ERR(root);
 
 	if (!group->cg_item.ci_name)
 		group->cg_item.ci_name = group->cg_item.ci_namebuf;
 
-	sd = configfs_sb->s_root->d_fsdata;
+	sd = root->d_fsdata;
 	link_group(to_config_group(sd->s_element), group);
 
-	mutex_lock(&configfs_sb->s_root->d_inode->i_mutex);
-
-	name.name = group->cg_item.ci_name;
-	name.len = strlen(name.name);
-	name.hash = full_name_hash(name.name, name.len);
+	mutex_lock_nested(&root->d_inode->i_mutex, I_MUTEX_PARENT);
 
 	err = -ENOMEM;
-	dentry = d_alloc(configfs_sb->s_root, &name);
-	if (!dentry)
-		goto out_release;
-
-	d_add(dentry, NULL);
-
-	err = configfs_attach_group(sd->s_element, &group->cg_item,
-				    dentry);
-	if (!err)
-		dentry = NULL;
-	else
-		d_delete(dentry);
+	dentry = d_alloc_name(root, group->cg_item.ci_name);
+	if (dentry) {
+		d_add(dentry, NULL);
+
+		err = configfs_attach_group(sd->s_element, &group->cg_item,
+					    dentry);
+		if (err) {
+			BUG_ON(dentry->d_inode);
+			d_drop(dentry);
+			dput(dentry);
+		} else {
+			spin_lock(&configfs_dirent_lock);
+			configfs_dir_set_ready(dentry->d_fsdata);
+			spin_unlock(&configfs_dirent_lock);
+		}
+	}
 
-	mutex_unlock(&configfs_sb->s_root->d_inode->i_mutex);
+	mutex_unlock(&root->d_inode->i_mutex);
 
-	if (dentry) {
-	    dput(dentry);
-out_release:
-	    unlink_group(group);
-	    configfs_release_fs();
+	if (err) {
+		unlink_group(group);
+		configfs_release_fs();
 	}
 
 	return err;
@@ -1073,24 +1696,31 @@ void configfs_unregister_subsystem(struct configfs_subsystem *subsys)
 {
 	struct config_group *group = &subsys->su_group;
 	struct dentry *dentry = group->cg_item.ci_dentry;
+	struct dentry *root = dentry->d_sb->s_root;
 
-	if (dentry->d_parent != configfs_sb->s_root) {
-		printk(KERN_ERR "configfs: Tried to unregister non-subsystem!\n");
+	if (dentry->d_parent != root) {
+		pr_err("Tried to unregister non-subsystem!\n");
 		return;
 	}
 
-	mutex_lock(&configfs_sb->s_root->d_inode->i_mutex);
-	mutex_lock(&dentry->d_inode->i_mutex);
-	if (configfs_detach_prep(dentry)) {
-		printk(KERN_ERR "configfs: Tried to unregister non-empty subsystem!\n");
+	mutex_lock_nested(&root->d_inode->i_mutex,
+			  I_MUTEX_PARENT);
+	mutex_lock_nested(&dentry->d_inode->i_mutex, I_MUTEX_CHILD);
+	mutex_lock(&configfs_symlink_mutex);
+	spin_lock(&configfs_dirent_lock);
+	if (configfs_detach_prep(dentry, NULL)) {
+		pr_err("Tried to unregister non-empty subsystem!\n");
 	}
+	spin_unlock(&configfs_dirent_lock);
+	mutex_unlock(&configfs_symlink_mutex);
 	configfs_detach_group(&group->cg_item);
 	dentry->d_inode->i_flags |= S_DEAD;
+	dont_mount(dentry);
 	mutex_unlock(&dentry->d_inode->i_mutex);
 
 	d_delete(dentry);
 
-	mutex_unlock(&configfs_sb->s_root->d_inode->i_mutex);
+	mutex_unlock(&root->d_inode->i_mutex);
 
 	dput(dentry);